

  fna = "OBS_ang_modis_ocean_T63_ANN.nc" 
  fnb = "OBS_ang_modis_land_T63_ANN.nc" 
  fnc = "OBS_ang_modis_T63_ANN.nc" 

  system("rm "+fnc) 

  fla = addfile(fna,"r") 
  flb = addfile(fnb,"r") 
  flc = addfile(fnc,"c") 

  va = fla->Angstrom_Exponent_1_Ocean_QA_Mean_Mean  
  vb = flb->Angstrom_Exponent_Land_QA_Mean_Mean 

  vc = va 
  vc = (/ where(ismissing(vb),va,vb) /) 

  flc->ANG_MODIS=vc  

